(CNN) Dutch prosecutors believe that the suspect in the Utrecht tram shooting that killed three people on Monday had a terrorist motive, but authorities are probing if this was combined with any "personal problems," according to a statement released on Thursday.
The suspect, previously identified as Turkish-born 37-year-old Gokmen Tanis, will appear in court on Friday accused of offenses of multiple murder or manslaughter with a terrorist objective, and threat with a terrorist objective, according to the statement.
"The investigation has now also provided indications that the suspect had not received any help from other persons during the shooting incident," the prosecutors' statement says.
"Furthermore, it is being investigated whether the accused acted solely for the sake of a terrorist motive, or whether his actions were based on personal problems in combination with radicalized ideas."
The Netherlands Institute for Forensic Psychiatry and Psychology will conduct an examination of the suspect, authorities said.
While the investigation is "still very much ongoing," no connection has yet been found between the suspect and the victims, the statement adds.
Another 40-year-old person who was arrested in connection to this incident on Tuesday is still being investigated for any links to the shooting, prosecutors added.
Dutch authorities uncovered potential terror motives behind the attack after finding a letter in a getaway car, police said on Tuesday.
"A terrorist motive is being seriously considered," Utrecht's police and public prosecutor said in a joint statement. "A letter found in the flight car and the nature of events give cause for this. Other motives are not excluded and are also being investigated." The contents of the letter have not yet been revealed.
Police also released further details about those killed and injured in the attack earlier this week; they identified the victims who died as a 19-year-old woman from Vianen, a 49-year-old man from Utrecht and a 28-year-old man also from Utrecht.
Three of those wounded -- a 20-year-old woman from Utrecht, a 74-year-old man from De Meern and a 21-year-old woman from Nieuwegein -- suffered serious injuries and remain in a critical condition.